Download Opal as a Java jar file (why Java? read this):

Opal.0.3.7.jar (you may need to right-click, then choose "save link as")

No need to unpack or make anything.
Source code is included in the jar.
You must have Java version 1.4.
Go read the documentation page for further instructions.



Previous Versions

Opal.0.3.6.jar
Opal.0.3.5.jar
Opal.0.3.4.jar
Opal.0.3.3.jar
Opal.0.3.2.jar
Opal.0.3.1.jar
Opal.0.3.0.jar

Opal was originally implemented as a C program (Why switch to Java? Read this).
Download opal as a zipped or tar/gzipped archive:

opal_0.2.0.tar.gz
opal_0.2.0.zip

To unpackage the files, run
   gzip -dc opal_0.2.0.tar.gz | tar -xvf -
or
   unzip opal_0.2.0.zip


To compile and run opal, do the following: 

cd alignalign
make all
cd ../opal
make all
./Opal -f your_file